JPS63285329A - Electronically controlled dynamic pressure bearing - Google Patents

Abstract

PURPOSE:To enable high rigidity, low vibration and high reliability extending over the whole rotational frequency by exciting an electromagnet of a magnetic bearing to generate repulsive force or attraction force in the axial direction or in the direction of shaft diameter, in a rotational frequency region lacking dynamic pressure. CONSTITUTION:A permanent magnet 51 magnetized in the radial and axial directions is provided on a part of a shaft 1, and an electromagnet 6 is disposed on a housing 3 confronting with the magnet. At the time of stopping, low rotational frequency or high rotational frequency under the shortage of lubrication, the electromagnet 6 is excited to generate lines of magnetic force 8, thereby repulsing and attracting the permanent magnet 51 on the shaft to keep a gap in a pressure chamber 4 constant. On the other hand, in a rotational frequency region where dynamic pressure is sufficiently increased, the electromagnet 6 is low-excited or non-excited not to increase over-current loss at the magnetic bearing portions 5, 6.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides accurate axial and/or radial position regulation of a shaft during rotation and rest, and low rotational speed or dynamic pressure during startup or stopping. This invention relates to a high-rigidity bearing that achieves stable and highly reliable rotational drive during fluctuations in speed.

The present invention relates to high-rigidity bearings, such as spindle motors of storage devices such as optical disks and magnetic disks, which require stable and highly reliable rotational drive even when starting and stopping or when external impact force is applied. It is something.

2. Description of the Related Art A conventional hydrodynamic bearing is a non-contact type bearing in which a fluid 4 such as air, oil, or grease is interposed between a shaft 1 and a housing 3, as shown in FIG. It is possible to achieve high performance such as high rigidity, low vibration, and long life in the high rotation speed range.

Problems to be Solved by the Invention As can be seen from the solid line in Figure 3, which shows the relationship between rotational speed and load capacity of this conventional hydrodynamic bearing, high Since no pressure is generated when the rotation speed is high, there is a problem that the position of the shaft cannot be maintained accurately. Therefore, when applied to the spindle motor of a storage device such as an optical disk or a magnetic disk, the positional deviation between the head and the recording information track becomes extremely small in the appropriate rotation speed range, resulting in high track density (high capacity). It has the advantage of being able to realize On the other hand, when starting or stopping or when an external impact force is applied, the shaft and the housing come into contact and damage to the bearing is likely to occur, resulting in a disadvantage that the reliability of the storage device is reduced.

Therefore, an object of the present invention is to maintain complete non-contact between the shaft and the housing even at low rotational speeds such as when starting and stopping, or when dynamic pressure fluctuates, thereby achieving high rigidity, low vibration, and high resistance at all rotational speeds. The objective is to provide a hydrodynamic bearing that achieves reliability.

Means for Solving the Problems In order to achieve the above object, the present invention provides a dynamic pressure bearing formed between a shaft and a housing, a magnetic material provided on a part of the shaft, and a hydrodynamic bearing formed between the shaft and the housing. A composite bearing is constructed with a magnetic bearing formed between an electromagnet installed in a part, and repulses in the axial direction or radial direction in rotation speed regions where dynamic pressure is insufficient, such as when starting and stopping rotation. Alternatively, the electromagnetic control is performed such that the electromagnet of the magnetic bearing is excited to generate an attractive force, and the electromagnet is kept under excitation or non-excitation in a rotational speed region where dynamic pressure increases.

The magnetic material provided on a part of the shaft of the present invention can be composed of a permanent magnet magnetized in the radial direction and/or axial direction of the shaft. This permanent magnet can be produced by magnetizing a magnetic material filled in a groove formed in the shaft, by embedding a divided ring-shaped or rod-shaped permanent magnet in a housing formed in the shaft, or by attaching it to the bottom of the shaft. Can be integrated with the shaft.

The magnetic material provided on a portion of the shaft may also be composed of a soft magnetic material disposed in the axial direction. This soft magnetic material can be attached to the shaft by embedding it in a housing formed by hollowing out the shaft.

In a preferred embodiment of the invention, a displacement gauge is provided to measure the amount of gap between the shaft and the housing. Generally, it is known that magnetic bearings that perform uncontrolled magnetic repulsion or attraction are subject to unstable operation due to large gap fluctuations. Therefore, in such a case, the excitation current may be automatically controlled with respect to a target value of the gap set in advance as a reference value, using the gap between the shaft and the housing obtained by the displacement meter as a control amount. The above-mentioned displacement meter uses capacitance, light, pressure, etc. as a principle for measuring the gap, that is, the gap amount.

Although this is common, any form or configuration may be used as long as it can measure the gap between the shaft and the housing.

Function As explained above, the electromagnetically controlled dynamic pressure bearing according to the present invention is equipped with a magnetic bearing composed of a permanent magnet or a soft magnetic material and an electromagnet, and uses magnetic repulsion or attraction to control dynamic pressure. The pressure chamber of the bearing can be secured with an appropriate clearance. Therefore, according to the present invention, it is possible to provide a bearing that has high rigidity, low vibration, labor saving, and long life in the entire rotation speed range.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to specific examples of the present invention with reference to the accompanying drawings.

FIG. 1 shows a conceptual diagram of an embodiment of an electromagnetically controlled hydrodynamic bearing according to the present invention. In this embodiment, a permanent magnet 5I magnetized in the radial direction and the axial direction (bottom of the shaft) is provided on a part of the shaft 1, and an electromagnet 6 is provided on the housing 3 side facing the permanent magnet 5I. Further, in this embodiment, a displacement meter 9 is provided near the electromagnet 6 to measure the gap between the shaft and the housing.

According to the embodiment described above, when the electromagnet 6 is at rest, at a low rotational speed, or at a high rotational speed under insufficient lubrication, the electromagnet 6 is excited to generate magnetic lines of force 8, and the permanent magnet 5 on the shaft side is excited.
By repelling or attracting 1, the gap in the pressure chamber 4 can be kept constant, making it possible to compensate for the lack of load capacity. Further, in a rotational speed range where the dynamic pressure is sufficiently high, it is effective to save labor by setting the electromagnet 6 to low excitation or non-excitation so that the eddy current loss of the magnetic bearing portion 5.6 does not increase.

If the relationship between the excitation of the electromagnet 6 and the rotational speed is set, for example, as shown by the broken line in FIG. 3, the load capacity of the bearing will be constant over the entire rotational speed due to the addition of dynamic pressure and magnetic force.

In addition, the number of permanent magnets 5, electromagnets 6, displacement meters 9,
The arrangement and the like may be set so as to obtain the above effects, and are not limited to this embodiment.

FIG. 2 is a conceptual diagram of an electromagnetically controlled hydrodynamic bearing according to another embodiment of the present invention. In this case, the soft magnetic material 5□ is mounted inside the shaft in the axial direction. The electromagnet 6 is arranged on the housing 3 side in a solenoid shape such that lines of magnetic force 8 are distributed in the axial direction. Therefore, when the electromagnet is excited, the shaft 1 is magnetized according to the lines of magnetic force 8, and the position of the shaft 1 is regulated in the radial direction of the shaft. Also, the position of axis 1 is VCM (Voice
Similarly to the principle of the electromagnet 6 (Co11 Motor), the position in the axial direction is regulated depending on the mounting position of the electromagnet 6 and the strength of excitation. With these, effects similar to those of the embodiment shown in FIG. 1 can be achieved.

Those skilled in the art will easily understand that the configuration according to the present invention is not limited to the above-described embodiments, and that the same effect can be obtained with any configuration of a dynamic pressure bearing to which electromagnetic control is applied. I can do it.

As described in detail, the electromagnetically controlled hydrodynamic bearing according to the present invention includes a hydrodynamic bearing formed between a shaft and a housing, a magnetic material provided on a part of the shaft, and a part of the housing. It has a composite bearing consisting of a magnetic bearing formed between an electromagnet installed in the axial direction or The electromagnet of the magnetic bearing is excited to generate repulsive or attractive force in the radial direction of the shaft, and electromagnetic control is performed such that it is not excited or not excited in the appropriate rotational speed range where dynamic pressure increases.

Therefore, problems with conventional hydrodynamic bearings such as inability to rotate (insufficient load capacity) and damage to the bearing due to static friction caused by contact between the shaft and the housing can be solved. This is because it is equipped with a magnetic bearing made of a permanent magnet or a soft magnetic material and an electromagnet, and uses magnetic repulsion or attraction to secure the pressure chamber of the dynamic pressure bearing with an appropriate gap. be. In addition, by incorporating electromagnetic control to reduce or de-energize in the rotation speed range where the load capacity on the hydrodynamic bearing side is sufficient, it solves the problem of eddy current loss during high-speed rotation, which is a problem with ordinary magnetic bearings. can do,. Therefore, according to the present invention, it is possible to provide a bearing that has high rigidity, low vibration, labor saving, and long life in the entire rotation speed range.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram of one embodiment of the electromagnetically controlled hydrodynamic bearing according to the present invention, Figure 1 is a conceptual diagram of another embodiment of the electromagnetically controlled hydrodynamic bearing according to the present invention, Load capacity (radial load) in hydrodynamic bearings
Fig. 10 is a diagram showing the relationship between rotational speed and rotation speed, where the solid line shows the case of a hydrodynamic bearing and the broken line shows the case of a magnetic bearing. Figure 100 is a diagram showing the basic configuration of a conventional hydrodynamic bearing. . (Symbols in the diagram) 1...Axis, 2...Group, 3...
Housing, 4... Pressure chamber, 51... Permanent magnet, 52... Soft magnetic material, 6... Electromagnet,
7... Coil terminal, 8... Lines of magnetic force, 9.
...Displacement meter, patent applicant Nippon Telegraph and Telephone Corporation Fig. 1 Fig. 4 Fig. 3 Fig. 2... Taffle Pug 4... Pressure chamber

Claims (4)

[Claims] (1) A hydrodynamic bearing formed between the shaft and the housing;
Rotation that has a magnetic bearing formed between a magnetic material provided in a part of the shaft and an electromagnet provided in a part of the housing, and that dynamic pressure is insufficient when starting or stopping rotation, etc. In several ranges, the electromagnet of the magnetic bearing is excited to generate a repulsive force or an attractive force in the axial direction or radial direction, and in the rotational speed range where dynamic pressure increases, the electromagnet is de-energized or de-energized. An electromagnetically controlled hydrodynamic bearing that is characterized by its control. (2) The electromagnetically controlled hydrodynamic bearing according to claim 1, wherein the magnetic material provided on a portion of the shaft is a permanent magnet magnetized in the radial direction of the shaft. (3) The electromagnetically controlled hydrodynamic bearing according to claim 1, wherein the magnetic material provided on a portion of the shaft is a soft magnetic material arranged in the axial direction. (4) The electromagnetically controlled dynamic pressure bearing according to claim 1, further comprising a displacement meter that measures the amount of gap between the shaft and the housing.